U world Bio/Biochem
Suppose a glucose residue from an unbranched portion of glycogen is metabolized in an astrocyte. If the proposed mechanism by which astrocytes provide energy for neurons is correct, which of the following metabolic reactions must occur for the astrocyte to convert this residue into a fuel for neurons? 1.Glucose-1-phosphate to glucose-6-phosphate 2.Glucose to glucose-6-phosphate 33-phosphoglycerate to 2-phosphoglycerate 4Pyruvate to acetyl-CoA 5Pyruvate to lactate
1.Glucose-1-phosphate to glucose-6-phosphate 3-phosphoglycerate to 2-phosphoglycerate 3Pyruvate to acetyl-CoA
Which of the following statements accurately describes the sphingolipids in Table 3? 1.They provide structure to biological membranes 2.They are primarily used for energy storage 3.They can be hydrolyzed to produce two fatty acids
1.They provide structure to biological membranes
how many daltons is an amino acid?
110 Da
If a frameshift mutation changes the number of amino acids in a protein from 591 to 626, the difference between molecular weights of the wild-type and mutant proteins would be closest to: 1 Kda 2 Kda 4 Kda 8 Kda
4
A kinetics experiment reveals that the enzyme fumarase catalyzes the dehydration of malate with a kcat of 900 s−1. If the substrate concentration is equal to the Km of the reaction, what is the reaction velocity when the enzyme concentration is 200 nM?
9.0 × 10^1 µM/s**The question says the concentration of fumarase [E] is 200 nM, and the kcat is 900 s−1. Multiplying these terms yields a Vmax of 180,000 nM/s, which is equivalent to 180 µM/s (1,000 nM = 1 µM). Per the derived equation, dividing Vmax by 2 yields a reaction rate V0 of 90 µM/s, which is equal to 9.0 × 101 µM/s.
Pentose Phosphate Pathway
A metabolic process that produces NADPH and ribose 5-phosphate for nucleotide synthesis.
Viroid
A plant pathogen composed of molecules of naked, circular RNA several hundred nucleotides long.
nuclear localization sequence
A sequence of amino acids (usually basic) that directs a protein to the nuclear envelope, where it is imported by a specific transport mechanism. Nuclear localization sequences signal for the transport of proteins such as transcription factors to the nucleus.
voltage-gated ion channels
A specialized ion channel that opens or closes in response to changes in membrane potential
Researchers isolate a protein that runs as a single band on a nonreducing SDS-PAGE gel but as two distinct bands on a reducing gel. The protein is most likely a: A. heteromultimer that formed in the oxidizing environment of the endoplasmic reticulum. B. heteromultimer that formed in the reducing environment of the cytosol. C. homomultimer that formed in the oxidizing environment of the endoplasmic reticulum. D. homomultimer that formed in the reducing environment of the cytosol.
A. heteromultimer that formed in the oxidizing environment of the endoplasmic reticulum.
Which neutrally charged functional group forms in an acid-catalyzed reaction between a secondary amine and a ketone? A.Enamine B.Nitrile C.Imine D.Alkene
A.Enamine
Researchers isolated peptidoglycan from a eukaryotic cell. The best explanation for this would be that: A.the eukaryotic cell is a host to a bacterial species containing peptidoglycan. B.peptidoglycan is a component of some eukaryotic cell walls. C.membranes within the eukaryotic cell contain peptidoglycan as a structural element. D.a virus with a protein coat containing peptidoglycan infected the eukaryotic cell.
A.the eukaryotic cell is a host to a bacterial species containing peptidoglycan.
DNA polymerase
After the damaged base is removed, DNA polymerase helps the correct base to pair with the opposite strand
retro virus
An RNA virus that reproduces by transcribing its RNA into DNA and then inserting the DNA into a cellular chromosome; and inportant class of cancer-causing viruses.
VEGF signaling also leads to the dilation of existing blood vessels. One function of vasodilation is to: A. increase body temperature in cold environments. B. increase blood flow to the intestines following a meal. C. decrease blood flow to the kidneys during dehydration. D. maintain blood pressure following an episode of fluid loss.
B. increase blood flow to the intestines following a meal.
Physicians researching a global hepatitis outbreak discover a new strain of hepatitis (HXV) by analyzing chromosomal DNA of patient's liver cells. They found that HXV has a +ssRNA genome and replicates through DNA intermediates. What characteristic best describes the new hepatitis virus? A.It integrates its retroviral +ssRNA into the host genome. B.It has reverse transcriptase function. C.It synthesizes a complementary RNA strand. D.It translates its own proteins
B.It has reverse transcriptase function. discovered a new strain of hepatitis (HXV) by ***analyzing chromosomal DNA of patient's liver cells*** = virus is a retrovirus because it integrated with the host genome (DNA)!!!
Which of the following molecules could decrease the activity of one or more Krebs cycle enzymes? A.Glucagon B.NADH C.Acetyl-CoA D.ADP
B.NADH
In neurons, action potential propagation occurs along the axon. The analogous structure in skeletal muscle fibers that enables action potential propagation is the: A.actin filament. B.transverse tubule. C.motor endplate. D.myelin sheath.
B.transverse tubule. transverse (T) tubules are specialized muscle fiber structures that facilitate action potential propagation throughout individual muscle fibers.
Y linked alleles susceptible to complete loss from the population due to random chance alone
Because the Y chromosome has the smallest effective population size, Y-linked alleles would be present at the lowest numbers in this population
some eukaryotic organisms have multiple TERT genes with high sequence similarity that are expressed at different times in the organism's life cycle. these genes could have arisen by: a. alternative splicing b. conjugation c.gene duplication d.transformation
C. genen duplication "multiple genes with highly similar sequences"
Acetylation of lysine residues in histones increases gene expression because: A.DNA is tightly bound to negatively charged amino acids on histones. B.the carboxyl oxygen atoms in acetyl groups form hydrogen bonds with nitrogenous bases. C.the salt bridges between charged amino acids and phosphate groups are disrupted. D.lysine residues in histones associate with positively charged phosphate groups in DNA.
C. the salt bridges between charged amino acids and phosphate groups are disrupted. Acetylation of histones involves the transfer of acetyl groups from acetyl coenzyme A to positively charged amino groups on lysine or arginine residues. This modification disrupts salt bridges by reducing the positive charge on histones, which allows DNA to unwind and become more accessible to transcription machinery. As a result, the acetylation of histones causes nucleosomes to relax and increases gene expression.
In an isolated population of 10,000 rabbits, 900 are homozygous for a recessive mutant Sp1 allele. Assuming the population is in Hardy-Weinberg equilibrium, what is the percentage of rabbits in the population that would be heterozygous for the mutant Sp1 allele? A. 9% B.21% C.42% D.70%
C.42% use harvey eq q^ 2= 900/10,000=0.09 Square root 0.09 q=0.3 Use p + q = 1 to calculate p: p+q=1 p=1−0.3=0.7 2pq=2(0.7)(0.3)=0.42
Amino acid catabolism releases nitrogen in the form of ammonia. In the liver, the urea cycle prepares ammonia for excretion. Which amino acid could undergo deamination to produce ammonia for the urea cycle? A.Lysine B.Arginine C.Glutamine D.Aspartate
C.Glutamine
During muscle contraction, the power stroke is the pivoting motion of the myosin head that pulls the actin filament inward to shorten the sarcomere. Given this, which of the following events most immediately precedes this power stroke motion? A.The binding of ATP to the myosin heads B.The hydrolysis of myosin-bound ATP C.The release of Pi from the myosin head D.The binding of Ca2+ to tropomyosin
C.The release of Pi from the myosin head The dissociation of Pi initiates the power stroke, which is the actual pivot of the actin-bound myosin head that drags the actin filament toward the center of the sarcomere. This directly results in shortening of the sarcomere. The release of ADP from the myosin head occurs at the end of the power stroke. The myosin head is now in its low-energy conformation.
Human cardiac muscle differs from skeletal muscle because it: A.appears striated. B.requires acetylcholine to contract. C.contains intercalated discs. D.contains cells with multiple nuclei.
C.contains intercalated discs. skeletal & cardiac muscle appears striated cardiac cells have no more than 2 nuclei
Compared to the blood flowing into the left ventricle, the blood flowing into the right ventricle: A.has a higher oxygen concentration. B.has a higher pH. C.is entering a cardiac chamber with thinner walls. D.is entering a cardiac chamber that contracts to produce higher pressure.
C.is entering a cardiac chamber with thinner walls.
A student analyzing dividing cells of a certain type under the microscope finds that each daughter cell produced contains half the number of chromosomes as its parent cell. Given this, cells of this type would most likely contain all of the following EXCEPT: A.peroxisomes. B.nuclear pore proteins. C.single-stranded genomes D.microtubules.
C.single-stranded genomes Eukaryotic cells can be distinguished by their unique characteristics. They have a genome with multiple linear chromosomes (double-stranded DNA). They also use meiosis as one mechanism of cell division (sexual reproduction), and they have membrane-bound organelle
A study indicates that endurance exercise performance is related to type 1 skeletal muscle fiber characteristics that allow for efficient performance of aerobic respiration to generate ATP for extended periods of time. Given this, which of the following characteristics is (are) most likely to be associated with type 1 skeletal muscle fibers? I. High mitochondrial density II. High numbers of capillaries around the muscle fiber III. High myoglobin concentration in the muscle fiber A.I only B.I and II only C.III only D.I, II, and III
D.I, II, and III Type 1 fibers are fatigue resistant, contract slowly, and use aerobic respiration as their primary method of ATP production. Consequently, compared with glycolytic fibers, type 1 fibers are much richer in mitochondria (Number I), the site where many enzymes involved in aerobic respiration reside. Type 1 fibers also have access to a continuous supply of oxygen (the final electron acceptor of aerobic respiration) through an extensive network of capillaries (Number II) that surround the muscle fiber. In addition, type 1 fibers appear red under the microscope due to high concentrations of myoglobin, a red-pigmented, oxygen-binding molecule that aids in delivery of oxygen to the muscle cell interior (Number III).
One function of endothelial cells is to: A.contract to increase blood pressure. B.line the inside of the gastrointestinal tract. C.bind sites of vascular damage to form clots. D.line the inside of blood vessels.
D.line the inside of blood vessels The endothelium is the one-cell-thick layer of specialized epithelial cells (ie, endothelial cells) that line the interior of the cardiovascular system, which includes the heart, arteries, capillaries, and veins.
DNA consists of deoxyribose sugars linked to nitrogen bases at the _________ carbon of the sugar. The __________________ carbons are linked to phosphate groups, which each link to the rest of the DNA backbone.
DNA consists of deoxyribose sugars linked to nitrogen bases at the 1′ carbon of the sugar. The 3′ and 5′ carbons are linked to phosphate groups, which each link to the rest of the DNA backbone.
Which of the following catabolic pathways directly produce both ATP (or GTP) and NADH? Fatty acid oxidation Glycolysis The Krebs cycle The electron transport chain
Glycolysis The Krebs cycle
conjugation
In bacteria, the direct transfer of DNA between two cells that are temporarily joined.
lactate is converted to pyruvate, and in the mitochondria...
In the mitochondria, pyruvate is converted to acetyl-CoA by decarboxylation (release of a carbon atom as CO2). Acetyl-CoA then reacts with oxaloacetate to enter the citric acid cycle. Within this cycle, another carbon atom is released as CO2 when isocitrate is converted to alpha-ketoglutarate, a third is released when alpha-ketoglutarate becomes succinyl-CoA. The carbons contributed by acetyl-CoA are ultimately released as CO2 in these steps over the course of several repetitions of the cycle. Therefore, the three carbon atoms that were initially in lactate are eventually removed by three decarboxylation events, and their metabolic fate is to be released as CO
Leptin increases...
Leptin increases fatty acid oxidation and decreases fatty acid synthesis. In contrast, leptin-resistant cells cannot increase fatty acid oxidation despite adequate leptin signaling. As a result, AMPK signaling cannot be activated by leptin, which leads to increased and uninhibited ACC activity, promoting fatty acid synthesis and reducing β-oxidation.
depolarization occurs via the influx of .....
Normally, depolarization occurs via the influx of positive ions (ie, Na+, Ca2+) into SA and AV nodal cells, increasing cell membrane potentials and generating APs. APs fired from the SA node travel through cardiac muscle cells of the atria, inducing atrial contraction and ventricular filling. At the AV node, relay of APs to ventricular cells is delayed, ensuring that ventricular filling is complete prior to ventricular contraction. Next, APs travel through both ventricles, causing them to contract and expel blood into the arteries.
Quaternary structure
Quaternary structure is the interaction of two or more polypeptide chains with each other and is stabilized by the same forces as tertiary structure
Reducing agents such as dithiothreitol are commonly used in gels to...
Reducing agents such as dithiothreitol are commonly used in gels to break disulfide bonds, not form them.
Secondary structure
Secondary structure is the set of local folds within a polypeptide and usually consists of α-helices and β-sheets. These structures are primarily stabilized by hydrogen bonds between the carbonyls and amides of the polypeptide backbone.
Sigma (σ) bonds
Sigma (σ) bonds, which are generally the first bond formed between atoms, are created when an electron pair is shared between the two atoms by an end-to-end overlap of their atomic orbitals along the internuclear axis. Because of the efficient overlap of the atomic orbitals, σ bonds tend to be stronger and very stable.
alternative splicing
Splicing of introns in a pre-mRNA that occurs in different ways, leading to different mRNAs that code for different proteins or protein isoforms. Increases the diversity of proteins.
Tertiary structure
Tertiary structure is the overall three-dimensional structure of the protein and is stabilized by interactions between R groups, including hydrogen bonding, ionic, and hydrophobic interactions as well as disulfide bonds.
The formation of a disulfide bond occurs through an....
The formation of a disulfide bond occurs through an oxidation-reduction reaction, in which the sulfur atoms of cysteine residues are initially in reduced form and become oxidized. For this reaction to occur, an oxidizing agent must be present.
tertiary structure
The third level of protein structure; the overall, three-dimensional shape of a polypeptide due to interactions of the R groups of the amino acids making up the chain. stabilized by side chain interactions
ligand-gated ion channel
Type of membrane receptor that has a region that can act as a "gate" when the receptor changes shape.
describe waxes
Waxes are lipid molecules that typically form soft solids that are malleable at room temperature. Most waxes are composed of two sets of long-chain hydrocarbons linked together through an ester group, which generally forms when a long-chain alcohol reacts with a long-chain fatty acid.
exonuclease
When the error is at either end of the DNA strand, the DNA backbone is cleaved by exonucleases,
ligase
a ligase enzyme catalyzes the formation of new phosphodiester bonds.
Which of the following molecules could participate in cell signaling without a second messenger?
a steroid
when cells contract mysoin binds to...
actin
N-linked carbohydrate chains
added to certain asparagine residues of proteins in the endoplasmic reticulum N-linked carbohydrate chains are added to certain asparagine residues of proteins in the endoplasmic reticulum.
reducing sugar
any monosaccharide with a hemiacetal ring
phosphate group
at a ph of 7 its 2 negative charges
motor endplate (axon terminal)
axon continues down the peripheral nerve to its termination of a muscle fiber
Pyruvate drawing
be able to recognize
increased environmental stress
can result in decreased fitness
loosing your ovaries would...
cause degeneration of breast tissue
primary structure
characterized by the covalent carbon-nitrogen linkages of peptide bonds
glycine
disrupts alpha helixes
endonucelase
endonucleases cleave phosphodiester bonds within a strand
hormones secreted adrenal medulla
epinephrine and norepinephrine
Phosphatidylserine
found on inside, flips to outside during apoptosis found in lipid membranes
starvation
gluconeogenesis occurs during starvation
Medium-chain acyl-CoA dehydrogenase (MCAD) is an enzyme involved in β-oxidation, and is encoded by the autosomal ACADM gene. MCAD deficiency is caused by a mutation in ACADM, and results in impaired ability to digest medium-chain fatty acids for energy, and in their subsequent accumulation. Which of the following interventions would best relieve the negative effects of MCAD deficiency?
high carbs & low fats
Which experimental procedure(s) must scientists use to determine Vmax and Km of an enzymatic reaction using the Michaelis-Menten model? i. They must ensure that:they only measure the initial reaction rate for each substrate concentration. ii. total enzyme concentration is much greater than the Km of the reaction. iii.each initial substrate concentration tested is much greater than enzyme concentration
i. They must ensure that:they only measure the initial reaction rate for each substrate concentration. iii.each initial substrate concentration tested is much greater than enzyme concentration
inhibiting phosphorolysis leads to
inhibiting phosphorolysis leads to decreased glycogen degradation.
hepatocytes
liver cells; produce bile, absorb and secrete nutrients like glucose, and secrete plasma proteins
Mesoderm
middle germ layer; develops into muscles, and much of the circulatory, reproductive, and excretory systems
Antibodies participate in _________
non-covalent protein-protein interactions (hydrogen bonds and ionic interatctions)
germline mutations
occur in germ cells (sperm or ova) and can be passed to one's children at conception
Ectoderm
outermost germ layer; produces sense organs, nerves, and outer layer of skin
pi (π) bonds
pi (π) bonds are created by the side-to-side overlap of p orbitals along a plane perpendicular to (ie, above and below) the internuclear axis. Because the overlap in electron density is not as efficient as for σ bonds, π bonds are weaker and not as stable as σ bonds. As a result, π bonds require less energy to break than σ bonds
transformation
process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria
2 electron domains
sp
3 electron domains
sp2
4 electron domains
sp3 hybridization
Coopertivity
substrate binds to one active site and makes all other active sites change shape ... this makes it more likely that the enzyme will bind to more substrates
Polyubiquitin tags
target defective or unnecessary proteins for destruction by the proteasome Polyubiquitin tags target defective or unnecessary proteins for destruction by the proteasome.
high Kcat/Km
the enzyme has a high efficiency
High Kcat
the enzyme has a high turnover rate
Endoderm
the inner germ layer that develops into the lining of the digestive and respiratory systems
anomeric carbon
the new chiral center formed in ring closure; it was the carbon containing the carbonyl in the straight-chain form
dynein (motor proteins)
they hydrolyze ATP and move toward the minus (-) end of the microtubule retrograde transport - towards the cell body
enzymes / catalysts impact a reactions..
transition state activation energy rate constant does not impact the equilibrium concentrations or delta G
Michaelis-Menten equation
v = (vmax [S])/(Km + [S])
Kinesin (motor protein)
•Moves toward the plus end of the microtubule anterograde transport- away from cell body
